Modeling of Velocity-dependent Frictional Resistance of a Capsule Robot Inside an Intestine

Abstract

A model is first built for predicting the velocity-dependent frictional resistance of a capsule robot that moves inside the intestine in the paper. The capsule robot plays a more and more important role in checking diseases in the intestine. This study aims to optimize the locomotion mechanism and the control strategy of the capsule robot. The model consists of three parts: environmental resistance, viscous friction, and Coulomb friction. Environmental resistance is induced by the stress due to the viscoelastic deformation of the intestinal wall. Viscous friction is analyzed according to the apparent viscosity of intestinal mucus. Coulomb friction is a product of the local contact pressure and the Coulomb friction coefficient. In order to analyze the effects of the intestinal deformation, a five-element model is used to describe the stress relaxation of the intestinal material. Experimental investigation is used to identify the model parameters with homemade physical simulation measurement system and fixtures. Finally, the model's validity is verified by experimental results. It is shown that the model predicting results can fit the experimental results well when the moving velocity of the capsule is lower than 20 mm/s. The R 2 of these two sets of data is 0.8769. But at a higher velocity, there are significant differences between the two results and the R 2 declines to 0.1666. The friction model is expected to be useful in the development of the medical equipment in the intestine and the study of biomechanics of the intestine.

A wireless platform forin vivomeasurement of resistance properties of the gastrointestinal tract

“…A common method to measure the resistance properties of the intestine is to impose a motion to a capsule mock-up inside the lumen and to measure the associated force profile (Wang & Meng 2010, Zhang et al 2012, Zhou et al 2013). An equivalent approach, schematically represented in Fig.…”

“…An extensive quantification of resistance properties of the different GI segments -outside the scope of this paper -can then be obtained by adopting the proposed methods. The same approach would also enable gathering reliable data for implementing realistic biomechanical models of the GI tract (Kim et al 2007, Bellini et al 2011, Zhang et al 2012, Zhou et al 2013). …”

Controlling multistability in a vibro-impact capsule system

“…The vibro-impact capsule system is a self-propelled mechanism moving rectilinearly under internal harmonic excitation when overcoming environmental resistance, which has practical applications in gastrointestinal endoscopy [23,24] and engineering pipeline inspection [25,26]. A previous study of a simpler version of the capsule model was carried out in [27,28], where the authors investigated the response of the model in various dynamical scenarios.…”

Experimental verification of the vibro-impact capsule model

“…For example, Gao et al [11] developed a magnetic propulsion system for driving capsule endoscope inside human body through external magnetic fields. A prototype of capsule robot propelled by internal interactive force and external friction was designed by Li et al [4], and its velocity-dependent frictional resistance inside intestine was investigated in [12]. However, the detailed study of dynamics of the capsule for such an application has not been undertaken, though it would be essential for design and prototyping.…”

“…The conducted bifurcation analysis indicates that the behaviour of the system is mainly periodic, and a fine tuning of the control parameters can significantly improve the performance of the system. Although the size of the experimental rig here is much larger than the prototypes in [4,12], the re-scaling could be done using the nondimensionalized parameters of the mathematical model so that the results presented in this paper could be used for prototype design and fabrication.…”